If consciousness then dies, the pure form now no longer exists anywhere, but it's effect would still act in the material world.

Concepts don't have an "effect" on the world (except through how they make conscious creatures behave); you've got it exactly backwards. A concept is a description of the world in a conscious mind, it is not a rule that the world follows. E=MC2 is a description of how the universe behaves. Einstein did not have to work out the equation before it went into effect, and the "pure" concept does not have to exist in some Platonic metaphysical plane for the universe to refer to every time matter and energy interact. The claim of most of us here is that concepts do not exist except in minds, and your Socratic questioning is not having much success changing that. To sum up, I think that you're conflating the word "concept" with the thing it describes and thus giving it too much weight.

The physical world obviously follows these rules. If I drop a pen, it falls. The rules exist in some sense. Where do they exist?

If they only exist in our minds as models, fine. But, why are they allowed to exist infinitely in time, like matter, but not in space, like matter. Are they special in some way?

If we take this argument, for example, and then consider how much special stuff there is, (infinity for example), then that would seem to be suggesting there is potentially more special stuff than real stuff. Monism starts to collapse here.

Not really. Let's say your name is Kevin. And there are several other Kevins. Does that mean the name Kevin exists separately to those people who have been named Kevin in the past and possibly the future? Is there an external "Kevin" that exists in space as a name?

The universe operates on a cause and effect basis. There is matter, and it moves. Everything else from there on in is simply conceptual ways to determine what causes and effects are in operation at any one time.